1. Field of the Invention
The present invention relates to developing devices and process cartridges to be used in electrophotographic image forming apparatuses.
2. Description of the Related Art
Conventionally, a process cartridge system is employed in an electrophotographic image forming apparatus using an electrophotographic imaging process. In the process cartridge system, an electrophotographic photosensitive member and a process unit that acts on the electrophotographic photosensitive member are integrated into a cartridge, and this cartridge is removably mounted to the apparatus body. The process cartridge system allows a user to perform maintenance work on the apparatus without calling a service technician, and thus the operability of the apparatus can greatly improve. Therefore, the process cartridge system is widely employed in electrophotographic image forming apparatuses. Alternatively, a development cartridge system is often employed particularly in multi-color electrophotographic image forming apparatuses. In the development cartridge system, for example, a developing unit of a process unit, except for an electrophotographic photosensitive member, is integrated into a cartridge, and this cartridge is removably mounted on the apparatus body. Such a system yields similar effects to those of the process cartridge system.
Such a process cartridge or a developing device to be used in an electrophotographic image forming apparatus has a configuration in which an elastic blade serving as a regulating member formed of metal, rubber, and the like abuts against a developing roller. Then, toner is made to pass through a gap in an abutment portion of the elastic blade against the developing roller to regulate the thickness of a toner layer, and thus a thin layer of toner is formed on the developing roller. In addition, friction in the abutment portion gives sufficient friction charges to the toner. If nonmagnetic toner is regulated by the elastic blade, a toner supply roller for supplying the toner onto the developing roller is provided along the axial direction of the developing roller. In such a developing roller and a toner supply roller, various techniques are implemented to suppress toner leakage from the developing device along the axial ends of the developing roller and the toner supply roller. For example, an outer peripheral surface of the developing roller is made to abut against end seals affixed respectively to both side surfaces, in the axial direction of the developing roller, of a development frame member, and thus toner leakage along the two ends of the developing roller is suppressed. Meanwhile, a rotational shaft of the toner supply roller extends externally from the development frame member through a center hole formed in a bush member that is fitted in a notch portion formed in a side surface of the development frame member. Then, the toner supply roller is fitted in a bearing hole provided in a bearing member that rotatably supports the developing roller and the toner supply roller.
Japanese Patent No. 3,524,114 discusses a configuration for suppressing toner leakage from both ends of a toner supply roller by disposing toner supply roller sealing members and bush sealing members. In this configuration, each toner supply roller sealing member is disposed on a location of a bearing member inside a bearing hole in the axial direction of the toner supply roller and facing a side surface of the development frame member, and each bush sealing member is disposed in the notch portion formed in the side surface in parallel to the bush member.
Japanese Patent Application Laid-Open No. 2001-255741 discusses a configuration for suppressing toner leakage from both ends of a toner supply roller by forming bush members to be fitted into notch portions formed in side surfaces of a development frame member by rubber or a resin material. In this configuration, a lip is integrated into an inner periphery of the center hole of the bush member, and the lip is slid on the shaft of the toner supply roller. Thus, the toner leakage from both ends of the toner supply roller is suppressed.
There is an increasing demand for a sealing configuration that can suppresses toner leakage more reliably and that is inexpensive and easy to assemble as a sealing configuration to suppress toner leakage from an end of the developing roller or a shaft portion of the toner supply roller in the process cartridge and the developing device described above.